Yang S, Lee D S, Chung C H, Cheong M Y, Lee C-J, Jung M W
Neuroscience Laboratory, Institute for Medical Sciences, Ajou University School of Medicine, Suwon 443-721, Korea.
Neuroscience. 2004;127(4):805-12. doi: 10.1016/j.neuroscience.2004.06.001.
Superficial layers of the entorhinal cortex (EC) relay the majority of cortical input projections to the hippocampus, whereas deep layers of the EC mediate a large portion of hippocampal output projections back to other cortical areas, suggesting a functional segregation between superficial and deep layers of the EC as input and output structures of the hippocampus, respectively. However, deep layers of the EC send associational projections to superficial layers, suggesting a potential interaction between neocortical input and hippocampus-processed output in superficial layers. This possibility was investigated by examining whether deep to superficial EC projections support long-term synaptic plasticity, and whether they interact with other pathways in superficial layers in rat medial EC slice preparations. Synaptic responses of the deep-to-superficial layer projections were verified based on field potential profiles, paired-pulse facilitation, physical separation between superficial and deep layers, and pharmacological manipulation. Long-term potentiation (LTP) was reliably induced in the deep-to-superficial layer projections by burst stimulations that emulated theta or sharp wave electroencephalogram (EEG),and it was blocked by an N-methyl-d-aspartate receptor antagonist (D-2-amino-5-phosphonopentanoic acid) and a calcium channel blocker (nifedipine). Prolonged low frequency stimulation induced long-term depression. A weak stimulation of deep layers, which induced a small degree of LTP by itself, generated a much larger degree of LTP when paired with a strong stimulation of superficial layers, indicating that the deep-to-superficial layer projections cooperate with other pathways in the superficial EC to enhance synaptic weights. Our results suggest that neocortical input and hippocampal output information are integrated in superficial layers of the EC.
内嗅皮层（EC）的浅层将大部分皮质输入投射传递至海马体，而EC的深层则介导大部分海马体输出投射返回其他皮质区域，这表明EC的浅层和深层之间存在功能分离，分别作为海马体的输入和输出结构。然而，EC的深层向浅层发送联合投射，这表明新皮质输入与海马体处理后的输出在浅层可能存在相互作用。通过研究从EC深层到浅层的投射是否支持长期突触可塑性，以及它们是否与大鼠内侧EC脑片制备中浅层的其他通路相互作用，来探究这种可能性。基于场电位分布、双脉冲易化、浅层和深层之间的物理分离以及药理学操作，验证了从深层到浅层投射的突触反应。通过模拟θ波或尖锐波脑电图（EEG）的爆发刺激，在从深层到浅层的投射中可靠地诱导出了长时程增强（LTP），并且它被N-甲基-D-天冬氨酸受体拮抗剂（D-2-氨基-5-磷酸戊酸）和钙通道阻滞剂（硝苯地平）阻断。长时间的低频刺激诱导了长时程抑制。对深层的微弱刺激本身仅诱导出小程度的LTP，但当与对浅层的强刺激配对时，会产生更大程度的LTP，这表明从深层到浅层的投射与浅层EC中的其他通路协同作用以增强突触权重。我们的结果表明，新皮质输入和海马体输出信息在EC的浅层整合。
